The threshold for the stimulation of breathing at altitude: physiological support for the aviation industry standard for aircraft pressurization

Orme, Daniel James (2019). The threshold for the stimulation of breathing at altitude: physiological support for the aviation industry standard for aircraft pressurization. University of Birmingham. M.Sc.

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Abstract

As aircraft ascend, cabin pressure is always maintained below an equivalent altitude of 8,000ft (~120mmHg O2, ~15.4% O2). The choice of 8,000ft is a compromise between engineering, fuel efficiency, cost, human comfort and human physiology (Aerospace Medical Association, 2008). The brain’s response to hypoxia is to stimulate breathing to counteract its effects. Currently, the threshold at which breathing is stimulated by hypoxia is inconsistent with cabin pressure regulations, being reported in 1947 by Dripps and Comroe, to be at a far higher altitude, at ~85mmHg O2 (~10% O2) (~17,500ft). This research team is unaware of any study, since 1947, that has tried to identify the ventilatory threshold to hypoxia. Using modern experimental methodology and statistical design this study reassesses the breathing threshold to hypoxia in 20 participants. This research indicates that breathing is more sensitive than previously demonstrated, with significant stimulation of breathing (by 1 L.min-1 ), combined with a significant lower PetCO2 (by 1 mmHg), being detectable at 15.2% oxygen (~121mmHg O2, ~7900ft).

Type of Work:

Thesis (Masters by Research > M.Sc.)

Award Type:

Masters by Research > M.Sc.

Supervisor(s):